1. Field of the Invention
The present invention relates to fixing device provided, for example, on an image forming apparatus and adapted to fix an image of a developing agent transferred to a sheet.
2. Description of the Related Art
This kind of fixing device includes a type adapted to set a pressure applying roller in pressure contact with a heating roller. A sheet with an image of a developing agent transferred thereto is fed to between the heating roller and the pressure applying roller and, by doing so, the image of the developing agent is heated/fused on a sheet and fixed. The heating roller comprises, for example, a metal roller and a tungsten halogen lamp, etc., provided within the metal roller.
Incidentally, the heating source of the tungsten halogen lamp, etc., once converting electric energy to light and heat, heats the metal roller with radiation heat and the heat efficiency is as low as about 60 to 70%. Therefore, it takes more time to start up the fixing operation and a longer wait time is required.
In order to shorten the start-up time, a fixing technique has been developed which uses an induction heating. For example, JPN PAT APPLN KOKAI PUBLICATION NO. 59-33476 discloses the techniques using a roller having a thin metal layer on the outer periphery of a cylinder-like ceramic and performing heating by passing an induction current through the thin metal layer of the roller with the use of a conductive coil. The terminals of the leader lines of the conductive coil are fixed by a fastening means, such as a fastening screw, to the output terminal of a circuit board for outputting a high frequency wave.
Incidentally, the induction heating technique is not restricted to the fixing device and also is adapted in a rice cooker, etc. Since, in the case of the rice cooker, there is almost no need for the maintenance of the induction heating device and its exchange, no problem arises even if the leader line terminals of the coil are fixed by the fastening means, such as the fastening screw, to the output terminals of the circuit board.
In the case of the fixing device, on the other hand, the maintenance and exchange are often necessary. In the case where the leader line terminals of the coil are fixed by the fastening means, such as the fastening screw, to the output terminals of the circuit board, it is necessary to, during the maintenance, exchange, etc., loosen or tighten the fastening means each time and it takes more time to do so.
Further, the tightening strength of the fastening means differs depending upon the operators and it is not possible to achieve a uniform tightening strength. And there is sometimes a possibility that the fastening means will come off if it is too loose and that the circuit board will be destroyed if the fastening means is too tight.
Further, a larger current is supplied and a contact resistance varies depending upon the tightening strength, there being a risk that there occurs a variation in the heating characteristic.
It is to be noted that the above-mentioned problem can be eliminated if the circuit board's output terminals and leader lines are detachably connected through a connector.
However, the conductive coil and leader line, being normally formed by twisting a plurality of (for example, 19) wires, are strong in rigidity. In the case where, therefore, the leader lines are connected in an excessively bent state, the reaction force of the leader line acts on a connection site between the output terminal and the connector, thus causing the connection site to be gradually loosened to bring it to a dangerous state. For this reason, it was usually not possible to connect the leader line's terminal of the conductive coil to the corresponding output terminal of the circuit board directly by a connector.
The present invention is achieved with the above situation in view and the object of the present invention is to provide a fixing device in which one end portion of a conductive connection member is fixed by a fastening means to the output terminal of the circuit board and the leader lines of the coil are detachably connected through a connector to the other end portion of the connection member to allow the attachment and detachment to be made between the output terminal and the leader line of the coil in one operation and, even if the connector is used, it is possible to maintain a better connection state between the output terminal and the leader line of the coil.